1. Field of the Invention
The invention relates to a process for converting a geminally substituted cyclopentadiene containing 2-6 substituents into a non-geminally substituted cyclopentadiene.
2. Description of Related Art
Cyclopentadiene compounds, both substituted and unsubstituted, are used widely as a starting material for preparing ligands in metal complexes having catalytic activity. As metals in these complexes use is made in particular of transition metals and lanthanides.
A geminally substituted cyclopentadiene is a cyclopentadiene containing two substituents, which are not identical to a hydrogen atom, on the sp.sup.3 carbon atom of the cyclopentadiene ring. These geminally substituted cyclopentadienes have the drawback that they cannot be converted into an aromatic anion by deprotonation. As a consequence, geminally substituted cyclopentadienes cannot be used as anionic ligand in the synthesis of metallocene catalysts.
Since direct alkylation of cyclopentadiene compounds is usually attended by geminal substitution (see Jutzi, Synthesis 1993, 684), there is a need for a process for converting a geminally substituted cyclopentadiene into a non-geminally substituted cyclopentadiene.